Here, we present an integrated approach
to the weakly viscoelastic
fluid printability assessment by using global dimensionless criteria
(DC). The problem was studied on a model semidiluted polyvinylpyrrolidone
water-based ink. For the study purpose, the ink composition was kept
as simple as possible. First, the solution density, viscosity, and
surface tension were determined. Obtained data were used for testing
limitations of DC printability diagrams already available for Newtonian
fluids. A replotted version of the original Kim and Baek’s
map was developed emphasizing the importance of surface tension in
the drop formation process. Another set of DC (e.g., Ec and De) was also used for a real evaluation of
the viscoelasticity effect on both jetting conditions and drop formation.
The polymer relaxation time as a crucial parameter for viscoelasticity
was shown to be calculated using the Kuhn segment length rather than
from Zimm and Rouse theories for diluted polymer systems. Then, a
two-dimensional diagram using four DC (Oh and De with Ec and El as parameters)
is proposed based on the famous McKinley’s work. The diagram
describes the interplay of possible forces responsible for filament
thinning and breakup processes. Obtained results were supported by
further experiments involving drop ejection and formation, determination
of critical polymer concentration, and others. The proposed diagram
promises a useful initial step in further investigations of viscoelasticity
of polymer compounds by inkjet printing.
A hybrid material reduced graphene oxide based organic nanocomposite was synthesized from graphite
by modified Hummers method, which is further chemically reduced to form reduced graphene oxide
(rGO) and with resorcinol through a solvothermal process a reduced graphene oxide-resorcinol (rGO-R)
nanocomposite was obtained. The synthesized materials surface morphology and structural
compositions were studied through X-ray diffraction (XRD) and scanning electron microscope (SEM)
and their optical properties were studied through UV-visible spectroscopy and photoluminescence.
The material was further used as a fluorescent chemosensor to detect cerium ion under aqueous
conditions. The rGO-R composite’s sensing abilities were studied by following parameters viz. pH,
reversibility, time and the interference of other probable competing ions. The sensing follows both the
photo-induced electron transfer and intramolecular charge transfer processes.
The present work investigates the NO2 sensing properties of acceptor-doped ferrite perovskite nanostructures. The Sr-doped BiFeO3 nanostructures were synthesized by a salt precursor-based modified pechini method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The synthesized materials were drop coated to fabricate chemoresistive gas sensors, delivering a maximum sensitivity of 5.2 towards 2 ppm NO2 at 260 °C. The recorded values of response and recovery time are 95 s and 280 s, respectively. The sensor based on Bi0.8Sr0.2FeO3–δ (BSFO) that was operated was shown to have a LOD (limit of detection) as low as 200 ppb. The sensor proved to be promising for repeatability and selectivity measurements, indicating that the Sr doping Bismuth ferrite could be a potentially competitive material for sensing applications. A relevant gas-sensing mechanism is also proposed based on the surface adsorption and reaction behavior of the material.
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